Level 8: A planet's shield

Electricity and magnetism · level 8 of 8 · rough age 17 and beyond (a guide for parents; anyone can start anywhere)

The last level puts the fields to work on a planetary scale. Charged particles spiral in magnetic fields; the solar wind pushes on every planet; Earth's field holds it off ten Earth radii out, while Mars, with no field, takes the wind almost on its upper air. You will see why a planet's dynamo can die, how fast Mars is losing its air today, and whether a magnet could shield astronauts on the way there.

Lesson	You will be able to
Charged particles in a field	Use \(F = qvB\) and find the radius of a particle's circle
The solar wind	Find the solar wind's density and pressure at Mars and at Earth
Magnetospheres	Find where a planet's field holds off the solar wind
Planetary dynamos	Explain what a dynamo needs and why Mars's stopped
How Mars lost its air	Use MAVEN's results to work out how Mars loses gas to space
Could a magnet shield astronauts?	Find the field needed to turn aside fast protons

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